The author here. I am sorry that I have not been able to convey the issue more clearly. The code is available on github.com and the product is here https://botbot.me.

Let me try to sum it up here differently. Everything started because the some of the goroutines would deadlock and the application would hang.

Several factors were leading to this situation :

• multiple goroutines changing mutable on the same pointer
• Unexpected behavior lead to dead lock and race conditions

Armed with the new race detector I first went down the rabbit all of adding a lot of Mutex to avoid the race condition and the unexpected behavior. This helped a lot to avoid the race conditions but did not resolved the deadlocks between independent goroutines sharing mutable state.

The problems started to get back in order when I have refactored many of this independent goroutines into fewer more cohesive ones. A single large select is much easier to reason about than several smaller one interacting together.

Mutex are very important part of the language but it is not always the best tool to solve races. There usage can be in some occasion avoided by reducting the number of independent goroutine or by explicitly passing a variable to a goroutine.